Planar fluorescent lamps are useful in many applications, including backlights for displays, such as liquid crystal. A common weakness in such fluorescent lamps is their lack of uniformity in light intensity across the entire planar lamp.
Some planar fluorescent lamps utilize a plasma discharge through a low pressure mercury vapor and buffer gas to produce ultraviolet energy. The ultraviolet energy excites a fluorescent material which converts the ultraviolet energy to visible light. To produce the low pressure plasma discharge, such lamps typically require a substantial minimum energy input. If the lamps are driven below the minimum energy input, the plasma discharge may not be formed, or may be highly non-uniform. Moreover, even with an energy input well above the minimum energy, the lamp may still be non-uniform in light intensity due to the lack of uniformity in the distribution of the plasma discharge.
As is known to those of ordinary skill in the art, the light intensity produced by the lamp is proportional to the electric current in the plasma discharge. If the plasma discharge is non-uniform, the light produced by the lamp will be non-uniform. Thus, it is desirable to produce a lamp with uniform current density in the plasma discharge. However, the conventional planar fluorescent lamp lacks such uniformity in the current density and thus lacks uniformity in light intensity.
Therefore, it can be appreciated that there is a significant need for a planar fluorescent lamp having a uniform light intensity. The present invention provides this, and other advantages, as will be apparent from the following description and accompanying figures.